This invention relates to the addition of trans-1,2-dichloroethylene (xe2x80x9ctrans-1,2xe2x80x9d) to hydrofluorocarbon (xe2x80x9cHFCxe2x80x9d) and/or pentane-based blowing agents to provide foam premixes having improved xe2x80x9cprocessabilityxe2x80x9d, that is, to provide foam premixes in which the blowing agents create a one phase system with the polyol and/or in which the blowing agents have improved solubility in the polyol and/or in which the vapor pressure of the premix is lowered, and/or in which the premix has a lowered viscosity.
Zero ODP (ozone depletion potential) compounds such as HFCs and pentanes have been identified as alternatives for chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) as foam blowing agents. However, unlike HCFC-141b (1,1-dichloro-1-fluoroethane), HFCs such as 1,1,1,3,3-pentafluoropropane (xe2x80x9c245faxe2x80x9d), 1,1,1,3,3-pentafluorobutane (xe2x80x9c365mfcxe2x80x9d) and 1,1,1,2-tetrafluoroethane (xe2x80x9c134axe2x80x9d) have limited miscibility with polyurethane raw materials such as polyols, especially polyester polyols. For hydrocarbons such as n-pentane and iso-pentane, their miscibility with polyols, especially polyester polyols, is also low. This low miscibility results in several undesirable processing problems, such as phase separation of the premix resulting in inconsistency in foam production, high viscosity with resulting emulsions and mixing difficulties, and high vapor pressures. What is thus needed is a means of overcoming these processing problems with the new blowing agent alternatives.
Trans-1,2 has been mentioned as a component of azeotrope-like blowing agent blends, as in U.S. Pat. No. 5,196,137, but its disclosure as a premix compatibilizing agent has not been disclosed.
A method for improving the processability of foam premixes containing HFC and/or pentane-based blowing agents in polyols (especially polyester polyols) is provided, which method comprises adding trans-1,2 to said premix in an amount effective to enhance the processability of the premix. Preferred HFCs include 245fa, 365mfc and 134a. Preferred pentanes include n-pentane and iso-pentane.